The present invention relates generally to the field of medical devices. More particularly, the present invention relates to a device and monitoring system for use in localized cooling of the brain.
Temperature is an important variable in determining the amount of neural damage resulting from an ischemic attack (Dietrich et al, 1990). Clinically, temperature is now deemed a significant, independent risk factor for stroke (Reith et al, 1996), as well as a contributing risk factor to other risk factors for stroke such as hypertension, cigarette smoking, atrial fibrillation, diabetes, and transient ischemic attacks etc. Therapeutically, the implementation of mild hypothermia (34-36xc2x0 C.) to stroke and head trauma patients is advocated as beneficial based on clinical studies (Kammersgaard et al, 2000; Schwab et al, 1997) and animal experiments indicating long term neural and behavioural benefits (Corbett and Thornhill, 2000; Colbourne and Corbett, 1994).
Clinically, whole body cooling of stroke patients has been tested with forced air cooling with the Bair Hugger Wrap and anesthesics (Kammersgaard et al, 2000) or with cooling from fans and alcohol washes (Schwab et al, 1997). Pethidine anesthestic is given to prevent shivering activation. These whole body-cooling techniques are generally effective in reducing core temperature but long term stroke outcome analysis is not yet known. More regionalized head cooling of head trauma and stroke patients has been attempted. Cooling helmets (previously cooled or having cooled water or air circulating through them) attempt to decrease brain temperature via conductive changes through the skull (Klatz and Goldman, 1995 in U.S. Pat. No. 5,913,885; Gunn and Gunn 1998 in PCT Patent Application WO98/56310). Cooling pillows for the head and neck region have also been devised to decrease the body temperature of the patient (Tsutomu and Koji, 1998 in Japanese Patent Publication 09-072152; Katsumitsu and Shinichi, 2000 in Japanese Patent Publication 10-250455). These extracranial cooling devices may take some time to internally cool the brain via convective (air) or conductive processes. Another approach (Schwartz, 1997) is to cool the brain directly via cooling the carotid arterial blood by way of a water perfused neck collar, or alternatively, cooling the oral cavity by way of a water perfused endotracheal tube.
It is important to decrease the brain temperature of suspected stroke and head trauma patients from a more internal source (eg. carotid arterial blood flowing to the brain) without unnecessarily cooling the whole patient, which will increase the chance of activating shivering mechanisms. Shivering increases body temperature, which is detrimental to the patient. In the pre-hospital setting, it would be beneficial if precise control of the magnitude a duration of the cold temperature being applied to the carotid region bilaterally could be monitored and documented. However, this is not current practice.
A number of publications relating to cooling the brain have clearly established that cooling the brain reduces damage after stroke or other head injury. Exemplary publications include Slade et al., 1999; and Corbett et al. 2000.
A variety of prior art devices have attempted to cool the head or portions thereof to avoid injury after trauma. Patents relating to such devices are discussed briefly below.
Chilling a subject""s head to cool the brain is an approach disclosed in a number of patent documents. U.S. Pat. No. 5,913,885 discloses a device and method for cooling the whole head. The device includes a helmet and a neck-supporting back plate. The helmet receives a chilled fluid from an external source, or is fully surrounded with inserts capable of endothermic reactivity. U.S. Pat. No. 5,957,964 discloses a cap with a plurality of pockets for receiving pre-filled pouches of coolant, such as ice. This device is used to cool the surface of the head adjacent the cap. U.S. Pat. No. 6,030,412 discloses a hood for covering the head, neck and upper back of a patient. A coolant source is either perfused through the hood, or a combination of endothermic reactants is provided in cavities of the hood. A chin-strap can be placed in the neck area for securing the hood to a subject""s head. U.S. Pat. No. 4,750,493 teaches a method of cooling the face, particulary the region adjacent the mandible. Topical cold packs are applied, incorporating ammonium nitrate pellets stored near a reservoir of water which can be combined to cause an endothermic reaction. U.S. Pat. No. 4,920,963 discloses a shroud for cooling the extracranial area of the head, including the face and mandible. The shroud contains exothermic reactants such as ammonium nitrate pellets.
The prior art devices incorporating cooling inserts generally suffer from the disadvantage that a large cooling insert is required. Surfaces of the head which are merely adjacent the brain are cooled, and thus much of the cooling effect from a large cooling insert provides superfluous cooling of the skin. Further, if a subject requires cooling over an extended period of time, replacement inserts may be required. It is inconvenient to maintain large replacement inserts in reverse for such situations. Cooling by conduction from the skull inward to the brain takes time.
Body cooling devises for use in conjunction with a thermostat or monitor have been disclosed. U.S. Pat. Nos. 4,566,455 and 5,897,581 disclose headwear for applying cold to the scalp. Scalp temperature is monitored, and the headwear has a temperature monitor pocket for holding sensors that are connected to a display. A chin-strap is used for fastening the headwear to the scalp, but the neck on chin area is not cooled. U.S. Pat. No. 5,486,204 teaches a method for inducing hypothermia to the head area after a head wound. Intravascular temperature is reduced in the whole body by cooling a subject with a cooling blanket set to 5xc2x0 C. A subject is monitored to have a body temperature maintained 32-33xc2x0 C. Whole body cooling is often accompanied by the negative effect of inducing shivering. U.S. Pat. No. 5,643,336 teaches a heating and cooling pad for treating the face and head with a fluid that is circulated through the pad, which is controlled by a thermostat.
Therapeutic devices for application to the neck are known. U.S. Pat. No. 4,783,866 discloses a therapy pillow having a cold pack that is contoured in a U-shape to provide intimate contact with the neck and generalized cooling to the neck, area. A pocket within the pillow is provided to fit a temperature retaining material such as a cold pack, which is also U-shaped. This device is bulky in the region behind a subject""s neck, and would need to be removed to facilitate such procedures as intubation in the pre-hospital setting.
U.S. Pat. No. 5,916,242 (to Schwartz) discloses a collar for cooling the brain by cooling blood flowing through the carotid arteries. A liquid coolant or gaseous refrigerant is perfused through the collar, and passes by the carotid arteries. However, this apparatus does not allow monitoring of the coolant temperature. Further, the apparatus disclosed in this document is not amenable to a pre-hospital setting, as the perfusate must be circulated by mechanical means, such as a pump. The device is intended for use with subjects admitted to a tertiary care hospital setting thus portability is not required but accurate monitoring should be maintained.
Review of the prior art indicates that there is a need for a device or system that cools the brain in conjunction with temperature monitoring system so as to regulate the cooling effect. There is a need for a device, which provides monitored localized cooling to the brain in a way that minimizes shivering and whole-body hypothermia. Such a device is particularly necessary in a pre-hospital setting, such as during transport in an emergency vehicle.
Further, the prior art devices are relatively bulky and uncomfortable. In the pre-hospital setting, for example when a subject is being transported to hospital after injury, there is a need for a device that is comfortable and respectful of the subject""s physical condition. In the case of injury to the brain induced by stroke, a subject may be transported to hospital over a long distance. Many such subjects are elderly and would find it uncomfortably, traumatic or even undignified to be encased in such devices as are dislosed in the prior art. Particularly, bulky helmet-like devices with circulating fluids or large cooling inserts are inappropriate for this reason. Further, the sheer size of the known devices prohibit them from becoming a standard item kept in a emergency vehicle, or in any other pre-hospital setting having a limited amount of storage space.
It is an object of the present invention to obviate or mitigate at least one disadvantage of previous devices and systems for cooling the brain after injury.
A brain cooling device is disclosed herein which is designed for use in a pre-hospital setting, such as an on-site emergency setting, in an ambulance or other emergency vehicle. A brain cooling system is also disclosed which includes a temperature sensor through which the brain cooling effect can be observed and/or regulated. Further, a method for cooling the brain using the device or system is disclosed.
According to the invention, there is provided a brain cooling device comprising an arch for placement around the neck of a subject, the arch having two terminal ends for placement adjacent the carotid arteries of a subject. The terminal ends are disposed so as not to block the airway of the subject. The device also has at least one pocket formed within either one or both terminal ends of the arch. A cold insert is removably retained within the pocket, and is capable of imparting a temperature lowering effect to the carotid artery so as to cool the brain of the subject. The device also includes a monitoring system with several sensors for placement on the body of a subject to detect surface body temperature changes indicative of brain cooling by the arch.
The invention further provides a brain cooling system comprising an arch for placement around the neck of a subject so as not to block the airway of the subject. At least one pocket is formed within the arch, the pocket being disposed adjacent to the carotid artery on one or both sides of neck on the subject. A cold insert can be removably retained within the pocket, and is capable of imparting a temperature lowering effect to the carotid artery of the subject so as to cool the blood entering the brain. The system further includes sensors for detecting surface body temperatures of the subject, with changes in the body temperature being indicative of brain cooling, and a digital display and read-out for indicating the temperature changes detected by the sensors.
The invention also provides a method of cooling the brain of a subject comprising the steps of placing the inventive device on the neck of a subject so as not to obstruct the airway of the subject, placing a cold insert in a pocket of the device, and replacing the cold insert when it is no longer imparting a cooling effect to the subject as identified by the skin sensors which are a part of the temperature monitoring system.
A further method falling within the scope of the invention is provided as method of cooling the brain of a subject comprising the steps of installing the brain cooling system of the invention on a subject. The system is installed so that the arch is on the neck of the subject in a manner that does not obstruct the airway of the subject, and one or more sensors are placed on the subject in regions of the body such as a neck, forehead or axilla. At least one cold insert is placed in a pocket of the arch and is replaced as needed when one or more sensors indicate that a cooling effect is no longer being imparted to the subject.
The inventive brain cooling device can be useful in reducing brain damage once a head or brain injury has been sustained, such as in stroke or head trauma caused by an accident. By cooling the brain to achieve either normothermia or mild hypothermia, brain damage can be minimized or reduced after such an injury. By localizing cooling to the carotid (neck) region instead of the whole head, shivering can be minimized. The invention allows quick cooling of the brain, yet because of the relatively small surface area of cold application, the invention minimizes the threat of rebound shivering, and reduces the requirement for prophylactic use of anesthetics. By monitoring the cooling to a desired temperature indicative of brain cooling, the brain damage following injury can be minimized.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.